As we officially enter Summer this week in the northern hemisphere, it’s a good time to revisit an article we wrote in 2011 about heat-related injuries.

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After reading our excerpt and later the full document from the the Serious Accident Investigation Factual Report for the hyperthermia fatality of Caleb Hamm on the CR 337 fire in Texas, we heard from Dr. Brent Ruby, who has completed studies on this exact issue, even having studied wildland firefighters while they were working on fires. In one of his studies he was monitoring a wildland firefighter outfitted with a core temperature monitor, an ambient temperature sensor, and a special Camelback hydration system that monitored his water intake. This firefighter experienced a heat-related illness, heat exhaustion, and had to be evacuated off the fireline by a helicopter. That was a terrible thing to happen to a firefighter, and I’m sure the researchers thought the same thing, but it was probably a once in a lifetime cornucopia of incredibly useful data. Dr. Ruby sent us this message, reprinted here with his permission:

I was bothered by the findings of the CR337 fatality report from the investigation team. There are issues within this case that are very similar to a published heat exhaustion case study we published recently (Wilderness and Environmental Medicine 22, 122-125, 2011, http://www.ncbi.nlm.nih.gov/pubmed/21664560). In this report, we document drinking behavior, activity patterns, skin and core temperatures in a subject that suffered heat exhaustion and required evacuation. The lessons learned from this research clearly indicate that the best protection against a heat injury is reducing work rate. [*the abstract from the study is below]

Aggressive hydration strategies are over-preached and may provide a false sense of protection. It should be emphasized that the autopsy report as described in the fatality report indicated no signs of dehydration or electrolyte imbalance. I have tried to push these concepts to crews and safety officers when I get a chance to speak to them at meetings. I was bothered by this fatality knowing that it is seemingly directly linked to some of our research findings. I have tried to emphasize this to anyone that will listen in the world of wildfire.

You can certainly review our website to gain a better understanding of the publications we have done from research with the WLFF http://www.umt.edu/wpem. We have a great deal of physiological data, hydration, energy demands of the job, importance of supplemental feedings, etc. from all our work over the years. This peer reviewed research provides objective, scientific evidence that can be used to to change or influence policy to enhance safety on the line.

Let me know if you have any questions.

Regards, Brent Ruby

Brent C. Ruby, Ph.D., FACSM

Director, Montana Center for Work Physiology and Exercise Metabolism, The University of Montana

High work output combined with high ambient temperatures caused heat exhaustion in a wildland firefighter despite high fluid intake.

Cuddy JS, Ruby BC.

Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, Missoula, MT 59812-1825, USA.

The purpose of this case study is to examine the physiological/behavioral factors leading up to heat exhaustion in a male wildland firefighter during wildland fire suppression. The participant (24 years old, 173 cm, 70 kg, and 3 years firefighting experience) experienced heat exhaustion following 7 hours of high ambient temperatures and arduous work on the fire line during the month of August. At the time of the heat-related incident (HRI), core temperature was 40.1 °C (104.2 °F) and skin temperature was 34.4 °C (93.9 °F). His work output averaged 1067 counts·min(-1) (arbitrary units for measuring activity) for the 7 hours prior to the HRI, a very high rate of work over an extended time period during wildfire suppression.

In the 2.5 hours leading up to the heat incident, he was exposed to a mean ambient temperature of 44.6 °C (112.3 °F), with a maximum temperature of 59.7 °C (139.5 °F). He consumed an average of 840 mL·h(-1) in the 7 hours leading up to the incident and took an average of 24 ± 11 drinks·h(-1) (total of 170 drinks). The combined effects of a high work rate and high ambient temperatures resulted in an elevated core temperature and a higher volume and frequency of drinking than typically seen in this population, ultimately ending in heat exhaustion and removal from the fire line.

The data demonstrate that heat-related incidents can occur even with aggressive fluid intake during wildland fire suppression.

Unfortunately, even though Dr. Ruby’s research is funded by taxpayers through the National Institutes of Health, the National Science Foundation, and the Department of Defense, taxpayers are blocked from seeing the full results unless they pay a fee to the privately owned company that published the paper. We have written before about the results of taxpayer-funded wildfire-related research being held hostage by private companies. Dr. Ruby told Wildfire Today that he will send a copy of his paper to individuals that write to him at brent dot ruby at mso dot umt dot edu

The combined information about the fatality of Caleb Hamm on the CR 337 fire and Dr. Ruby’s study on wildland firefighters, is shocking. From the abstract, again:

The data demonstrate that heat-related incidents can occur even with aggressive fluid intake during wildland fire suppression.

Working on a wildfire on a hot day can lead to heat exhaustion and hyperthermia, and can be fatal EVEN IF a person drinks plenty of water and is not dehydrated.

Symptoms and prevention

We asked Dr. Ruby for more information:

Exertional hyperthermia occurs when the metabolic heat production from hard work overwhelms the bodies ability to off load it to the environment. This unloading can be blocked by clothing and/or slowed due to high radiant heat from the sun or an adjacent fire.

The best approach [to prevent heat exhaustion and hyperthermia] is to know thyself and thy physical limits. Establishing a pace schedule that allows temperature to come back down in between periods of work that result in a rise in temperature. The factors of importance are pace, fitness level for the task at hand, hydration behaviors and simultaneously electrolyte concentrations in the blood.

It is important for wildland firefighters to drink plenty of water, but this will not, by itself, totally eliminate all chances of heat-related illness.

Be careful out there.

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UPDATE October 27, 2011:

Dr. Ruby sent us the following list of other publications on similar topics that are in peer reviewed journals. I assume that most of them are not available to the public (don’t get me started on that again!) unless you pay the ransom fees at the private companies, or send a message to Dr. Ruby: brent dot ruby at mso dot umt dot edu

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UPDATE October 28, 2011:

The U.S. National Library of Medicine has an excellent article about heatstroke, which can follow heat cramps and heat exhaustion and is life-threatening. The article includes causes, symptoms, first aid, what not to do, when to call 911, and prevention (including “avoid exercise or strenuous physical activity outside during hot or humid weather”. Good luck with that one, firefighters.)

10 thoughts on “The myth of drinking water”

Please allow me to comment, as I am Caleb’s mother, and as you can imagine, I very closely watch any news/info about his death.
If you will read the SAIR, my son spoke up and said he was ill as early as 11 a.m. that day. This was disregarded. No medical attention was sought for him. He was instead told to rest, and was left alone. He stumbled into a ravine and lay, dying. He never made it out of that ravine.
Yes, all the warnings and research will simply fall on deaf ears unless the BLM changes the mode of work it expects from these hardworking and driven individuals.
If you will also read the report made by the CDC about Caleb’s death, you will find even the military has stringent work duties in extreme heat.
Also, according to the toxicology report from his autopsy, he did not have caffeine or any other foreign substance in his body. Can be verified.
Have tried numerous times for someone from BLM to meet with me about my son’s death. To date, NO ONE will. NO ONE will answer my questions as to how/why no medical attention was sought for my son until after he was dead.
Forever Caleb’s mother
LYNNETTE HAMM

Happened to me on a fire on Cabeza Prieta NWR. I was so weak I couldn’t stand without help and they said I was talking gibberish. I was one of the two EMTs on the fire as well. Flew me back to spike camp and set me in a pickup with A/C and water/Gatorade for a few hours and that was the extent of my treatment. Got it again 2 years later as a structural ff on a day temps were 105-107 and humidity was high. It ain’t no fun.

Respectively I would like to first speak to Mrs. Hamm, Caleb’s mother. I believe the loss of a child is probably the worst event that can occur to a person. It is something that I hope I will never have to entirely understand.
I hope someday you will find closure in regards to your son’s passing. Tonight our thoughts and prayers are with you.

Last year at the North East Fire Supervisor’s meeting I had the opportunity to hear Dr. Ruby speak. I found him interesting and actually entertaining. Here’s my take always from his talk:

Early season aerobic fitness is the best protection for firefighters.

Less experienced people are at higher risk.

If you provide cold fluids it’s just as advantages as large amounts of room temperature fluids.

Perhaps it’s time to seek legal representation since the BLM isn’t cooperating with you. That’s so completely absurd they’re treating you this way. Hiding the truth that many crews still participate in some form of hazing. I also think too many agency folks truly don’t recognize the signs and symptoms of heat related illnesses. We just sent 2 guys within an hour of each other to a local hospital during an IA fire of which I was the IC. Both FF’s are new this season, one of which is on my engine. I don’t mess around with heat related illness on the fireline. Both FF’s were released that evening and back on the line the following day.

I am not a medical professional but did work as a EMT in an outside environment in hot areas and as a firefighter on the line. These are observations, not scientific facts.

As the ambient temperature gets close to that of a humans normal temperature cooling become more and more difficult and an individuals tolerance and ability to compensate varies from person to person.

Individuals can become adjusted to hot environments become heat tolerant, but a some point it just becomes too hot to continue working.

One solution is to move to a cooler environment and reduce activity. That what the locals and wild life do.

While working in the Southwest over a couple of years supervisors approved a revised work schedule of either a very early morning 5am work start or a split day early morning late afternoon/evening out side work outside schedules. Fires and out urgent events/emergencies don’t always respect such schedules.

Careful determination of values at risk and the hourly condition of fire fighters in hot weather needs to be constantly evaluated. In aviation operations temperatures play a key role in operations and even small changes can have a profound effect.

Recovery from near or actual heat exhaustion can vary from person to person but I often found even when in my prime physical condition it could take from 8 to 24 hours in a cool environment.

After reading this I thought of two things right away. First one would be we still need to drink plenty of fluids. I hope others don’t read this and think that drinking is not important, it is. There have been many cases of firefighters going down due to not drinking enough. Second would be the firefighter mentality. Just about all firefighters have a mind set of go… go… go. Often it is “I don’t want to be the one that needs a break” People, we all need a break and if you are a supervisor you should make sure they are taking them. The cool down time is just as important as water intake.

Findings not being discounted, but everyone is different. Some people require more water to function, others less. Forcing people to conform to something other than what is right for them sometimes causes more harm than good.

I find that, personally, almost nothing beats salt tablets [with sufficient water]. I learned of them in boot camp at Camp Lejeune, SC in 1965, where they were routinely distributed to us trainees. Got to pace ourselves in any event.

My sincere condolences to Mrs. Hamm. There should be more oversight of ff’s in the heat.